Preheating of chemical vapor deposition precursors

ABSTRACT

Chemical vapor deposition systems include elements to preheat reactant gases prior to reacting the gases to form layers of a material on a substrate, which provides devices and systems with deposited layers substantially free of residual compounds from the reaction process. Heating reactant gases prior to introduction to a reaction chamber may be used to improve physical characteristics of the resulting deposited layer, to improve the physical characteristics of the underlying substrate and/or to improve the thermal budget available for subsequent processing. One example includes the formation of a titanium nitride layer substantially free of ammonium chloride using reactant gases containing a titanium tetrachloride precursor and a ammonia precursor.

[0001] This application is a Divisional of U.S. application Ser. No.09/642,976, filed Aug. 18, 2000 which is incorporated herein byreference.

TECHNICAL FIELD

[0002] The present invention relates generally to chemical vapordeposition, and in particular to methods for chemical vapor depositionincluding preheating of the chemical vapor deposition precursors,systems to perform the methods, and apparatus produced by such methods.

BACKGROUND

[0003] Semiconductor integrated circuits (ICs) contain individualdevices that are typically coupled together using metal lineinterconnects and various contacts. In many applications, the metallines are formed on a different level than the devices, separated by anintermetal dielectric, such as silicon oxide or borophosphosilicateglass (BPSG). Commonly used metal lines include aluminum, tungsten andcopper, as well as combinations of these materials with refractorymetals and silicon. Interconnects used to electrically couple devicesand metal lines are formed between the individual devices and the metallines. A typical interconnect is composed of a contact hole (i.e.opening) formed in an intermetal dielectric layer over an active deviceregion. The contact hole is often filled with a metal, such as aluminumor tungsten.

[0004] Interconnects often further contain a diffusion barrier layersandwiched between the interconnect metal and the active device regionat the bottom of the contact hole. Such layers prevent intermixing ofthe metal and the material from the active device region, such assilicon. Reducing intermixing generally extends the life of the device.Passive titanium nitride (TiN) layers are commonly used as diffusionbarrier layers. An example may include the use of titanium nitrideinterposed between a silicide contact and a metal fill within a contacthole. Further uses of diffusion barrier layers may include a barrierlayer interposed between a polysilicon layer and a metal layer in a gatestack of a field effect transistor.

[0005] Titanium nitride is a desirable barrier layer because it is animpermeable barrier for silicon, and because it presents a high barrierto the diffusion of other impurities. Titanium nitride has relativelyhigh chemical and thermodynamic stability and a relatively lowresistivity. Titanium nitride layers are also often used as adhesionlayers, such as for tungsten films. While titanium nitride can be formedon the substrate by physical vapor deposition (PVD) or chemical vapordeposition (CVD) techniques, CVD is often the technique of choice.

[0006] CVD is a process in which a deposition surface is contacted withvapors of volatile chemical compounds, generally at elevatedtemperatures. The compounds, or CVD precursors, are reduced ordissociated at the deposition surface, resulting in an adherent coatingof a preselected composition. In contrast to physical deposition, CVDdoes not require high vacuum systems and permits a wide variety ofprocessing environments, including low pressure through atmosphericpressure, and is an accepted method for depositing homogeneous filmsover large areas and on non-planar surfaces.

[0007] CVD is often classified into various types in accordance with theheating method, gas pressure, and/or chemical reaction. For example,conventional CVD methods include cold-wall CVD, in which only adeposition substrate is heated; hot-wall CVD, in which an entirereaction chamber is heated; atmospheric CVD, in which reaction occurs ata pressure of about one atmosphere; low-pressure CVD (LPCVD) in whichreaction occurs at pressures from about 10⁻¹ to 100 torr; andplasma-assisted CVD (PACVD) and photo-assisted CVD in which the energyfrom a plasma or a light source activates the precursor to allowdepositions at reduced substrate temperatures. Other classifications areknown in the art.

[0008] In a typical CVD process, the substrate on which deposition is tooccur is placed in a reaction chamber, and is heated to a temperaturesufficient to drive the desired reaction. The reactant gases containingthe CVD precursors are introduced into the reaction chamber where theprecursors are transported to, and subsequently adsorbed on, thedeposition surface. Surface reactions deposit nonvolatile reactionproducts on the deposition surface. Volatile reaction products are thenevacuated or exhausted from the reaction chamber. While it is generallytrue that the nonvolatile reaction products are deposited on thedeposition surface, and that volatile reaction products are removed, therealities of industrial processing recognize that undesirable volatilereaction products, as well as nonvolatile reaction products fromsecondary or side reactions, may be incorporated into the depositedlayer. Integrated circuit fabrication generally includes the depositionof a variety of material layers on a substrate, and CVD may used todeposit one or more of these layers.

[0009] As an example, one LPCVD process combines titanium tetrachloride(TiCl₄) and ammonia (NH₃) to deposit titanium nitride. However, LPCVDtitanium nitride using these precursors has a tendency to incorporate alarge amount of residual ammonium chloride in the film. This residualammonium chloride detrimentally effects the resistivity and barrierproperties of the titanium nitride layer. Once exposed to air, theresidual ammonium chloride will cause the titanium nitride layer toabsorb water and to form particles, both undesirable effects. It isknown that residual ammonium chloride can be reduced by the use ofammonia post-flow, or annealing in an ammonia atmosphere, subsequent todeposition. However, such post-processing leads to reduced throughputand a higher risk of particle formation. It is also known that increasedreaction temperatures can be used to reduce the incorporation ofresidual ammonium chloride. However, this, too, is detrimental asincreased processing temperatures reduce the thermal budget availablefor subsequent processing and often lead to undesirable dopantdiffusion.

[0010] For the reasons stated above, and for other reasons stated belowwhich will become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a need in the art foralternative methods of chemical vapor deposition.

SUMMARY

[0011] The various embodiments of the invention include chemical vapordeposition methods, chemical vapor deposition systems to perform themethods, and apparatus produced by such chemical vapor depositionmethods. The methods involve preheating one or more of the reactantgases used to form a deposited layer. The reactant gases contain atleast one chemical vapor deposition precursor. Heating one or more ofthe reactant gases prior to introduction to the reaction chamber may beused to improve physical characteristics of the resulting depositedlayer, to improve the physical characteristics of the underlyingsubstrate and/or to improve the thermal budget available for subsequentprocessing. One example includes the formation of a titanium nitridelayer with reactant gases containing the precursors of titaniumtetrachloride and ammonia. Preheating the reactant gases containingtitanium tetrachloride and ammonia can reduce ammonium chloride impuritylevels in the resulting titanium nitride layer, thereby reducing oreliminating the need for post-processing to remove the ammonium chlorideimpurity.

[0012] For one embodiment, the invention provides a method of depositinga layer of material on a substrate. The method includes heating areactant gas containing at least one chemical vapor deposition precursorto a temperature within approximately 150° C. of an auto-reactiontemperature of each chemical vapor deposition precursor of the reactantgas, introducing the heated reactant gas to a reaction chambercontaining the substrate, and reacting the reactant gas in the reactionchamber. Reacting the reactant gas involves reaction of the chemicalvapor deposition precursors to deposit the layer of material on thesubstrate. It is recognized that additional compounds may beincorporated into the layer of material, such as nonvolatile reactionproducts from side reactions deposited in the layer of material as wellas volatile reaction products from desired or side reaction productsentrapped in the layer of material.

[0013] For another embodiment, the invention provides a method ofdepositing a layer of material on a substrate. The method includesheating a reactant gas containing at least one chemical vapor depositionprecursor to a temperature below an auto-reaction temperature of eachchemical vapor deposition precursor of the reactant gas, combining theheated reactant gas and at least one additional reactant gas,introducing the combined gases to a reaction chamber containing thesubstrate, and reacting the combined gases in the reaction chamber.Reacting the combined gases deposits at least the layer of material onthe substrate. For yet another embodiment, the additional reactant gasesare also heated prior to introduction to the reaction chamber.

[0014] For a further embodiment, the invention provides a method ofdepositing a layer of titanium nitride on a substrate. The methodincludes heating a first reactant gas containing titanium tetrachlorideto a first temperature and heating a second reactant gas containingammonia to a second temperature. The first and second temperatures areeach below an auto-reaction temperature of titanium tetrachloride andammonia. The method further includes combining the heated first andsecond reactant gases, introducing the combined first and secondreactant gases to a reaction chamber containing the substrate, reactingthe first and second reactant gases in the reaction chamber to producetitanium nitride, and depositing the titanium nitride on the substrate.

[0015] For another embodiment, the invention provides a chemical vapordeposition system. The chemical vapor deposition system includes a gassource, a reaction chamber, a gas conduit coupled between the gas sourceand the reaction chamber, a heater, a gas flow temperature sensorcoupled to the gas conduit between the heater and the reaction chamber,and a control system coupled to the gas flow temperature sensor and theheater. The control system is adapted to adjust energy input from theheater to the gas conduit in response to data from the gas flowtemperature sensor. For yet another embodiment, the chemical vapordeposition system further includes a gas flow control valve coupled tothe gas conduit. For this embodiment, the control system is furthercoupled to the gas flow control valve and is further adapted to controlan opening of the gas flow control valve in response to data from thegas flow temperature sensor.

[0016] Further embodiments of the invention include deposition methodsand chemical vapor deposition systems of varying scope, as well asapparatus making use of such deposition methods and chemical vapordeposition systems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic block diagram of one embodiment of achemical vapor deposition system.

[0018]FIG. 2 is an elevation view of one embodiment of a wafercontaining semiconductor dies.

[0019]FIG. 3 is a block diagram of one embodiment of an integratedcircuit memory device.

[0020]FIG. 4 is a block diagram of one embodiment of an exemplarycircuit module.

[0021]FIG. 5 is a block diagram of one embodiment of an exemplary memorymodule.

[0022]FIG. 6 is a block diagram of one embodiment of an exemplaryelectronic system.

[0023]FIG. 7 is a block diagram of one embodiment of an exemplary memorysystem.

[0024]FIG. 8 is a block diagram of one embodiment of an exemplarycomputer system.

DESCRIPTION OF THE EMBODIMENTS

[0025] In the following detailed description of the preferredembodiments, reference is made to the accompanying drawings which form apart hereof, and in which is shown by way of illustration specificembodiments in which the inventions may be practiced. These embodimentsare described in sufficient detail to enable those skilled in the art topractice the invention, and it is to be understood that otherembodiments may be utilized and that process or mechanical changes maybe made without departing from the scope of the present invention. Theterms wafer and substrate used in the following description include anybase semiconductor structure. Both are to be understood as includingsilicon-on-sapphire (SOS) technology, silicon-on-insulator (SOI)technology, thin film transistor (TFT) technology, doped and undopedsemiconductors, epitaxial layers of a silicon supported by a basesemiconductor structure, as well as other semiconductor structures wellknown to one skilled in the art. Furthermore, when reference is made toa wafer or substrate in the following description, previous processsteps may have been utilized to form regions/junctions in the basesemiconductor structure, and terms wafer or substrate include theunderlying layers containing such regions/junctions. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the present invention is defined only by the appendedclaims and equivalents thereof.

[0026]FIG. 1 shows a simplified schematic block diagram illustrating oneembodiment of a Chemical Vapor Deposition (CVD) system 100 in accordancewith the invention. It is to be understood that the CVD system 100 hasbeen simplified to illustrate only those aspects of the CVD system 100relevant for a clear understanding of the present invention, whileeliminating, for the purposes of clarity, many of the elements found ina typical CVD system 100. Those of ordinary skill in the art willrecognize that other elements are required, or at least desirable, toproduce an operational CVD system 100. However, because such elementsare well known in the art, and because they do not relate to the designwhich is the subject of the various embodiments, a discussion of suchelements is not provided herein.

[0027] The design and construction of CVD systems is well known, and thepresent invention is applicable to any CVD system. The CVD system 100for one embodiment comprises a cold wall reaction chamber 112, typicallyconstructed of stainless steel. The bottom and sides of the reactionchamber 112 may be lined with quartz to protect the walls from filmdeposition during the processing steps. The walls of the reactionchamber 112 may be cooled by a circulating water jacket (not shown) inconjunction with a heat exchanger (not shown). The walls are generallymaintained at or below 100° C., because higher temperatures may inducethe deposition of films on the walls of the reaction chamber 112. Suchdepositions are undesirable because they absorb energy and effect heatdistribution within the reaction chamber 112, causing temperaturegradients which adversely affect the processing steps. Furthermore,depositions on walls may flake and produce particulates that cancontaminate a wafer in the reaction chamber 112. However, such coolingof the walls of the reaction chamber 112 is within the discretion of thedesigner.

[0028] A wafer support table 114 or the like is located near the bottomof the reaction chamber 112, and is used for supporting a wafer orsubstrate 116. The support table 114 is generally a flat surface,typically having three or more vertical support pins 115 with lowthermal mass. The support table 114 may be heated to help reducetemperature variations on the supported substrate 116.

[0029] A wafer handling system 118 is adjacent to the reaction chamber112, and includes a wafer cassette 120 and a wafer handler 122. Thewafer cassette 120 holds a plurality of wafers (substrates 116), and thewafer handler 122 transports one wafer at a time from the wafer cassette120 to the wafer support table 114, and back again. A door 124 isolatesthe wafer handling system 118 from the reaction chamber 112 when thewafers are not being transported to and from the wafer support table114.

[0030] A showerhead 126 introduces reactant gases 127 into the reactionchamber 112, and a plurality of light sources 128 heat the substrate116. For the purposes of this description, the embodiment will bedescribed in terms of light sources 128, although other sources ofheating a substrate 116, such as RF and microwave energy, are known andapplicable to the present invention. In addition, the showerhead 126 isdepicted to be above the surface of substrate 116, although showerhead126 may optionally be disposed to the side of substrate 116 as well asunderneath substrate 116. Furthermore, distribution devices other thanshowerhead 126 may be used to introduce and distribute reactant gases127 to the reaction chamber 112.

[0031] One or more gas sources 130A-B are coupled to the showerhead 126to provide one or more of the reactant gases 127 to be disbursed by theshowerhead 126 within the reaction chamber 112. More than one type ofgas may be available from each gas source 130, and reactant gases 127may be provided to the showerhead 126 individually or in combination.

[0032] Each reactant gas includes at least one CVD precursor. Examplesof CVD precursors include titanium tetrachloride and ammonia. Theseprecursors can be combined to deposit titanium nitride. In a pyrolysissystem, the reactant gases may require only one CVD precursor. Anexample of such a system includes silane (SiH₄) which can be used todeposit silicon (Si) without further precursors. Although the term“reactant gas” is used, one or more of the reactant gases 127 mayinclude a carrier, or non-reactive, gas. Examples of carrier gasesinclude nitrogen (N₂), argon (Ar), helium (He), and other non-reactivegases used in the art of chemical vapor deposition. CVD system 100 mayfurther include additional gas sources providing only carrier gases.

[0033] Gas flow control valves 132A and 132B control the flow of gasesfrom gas sources 130A and 130B, respectively, through gas conduits 133Aand 133B, respectively. Gas conduits represent a flow path for thereactant gases 127 between the gas sources 130 and the reaction chamber112. Gas conduits include such things as piping between elements of theCVD system 100 as well as spaces or channels for gas flow withinelements of the CVD system 100. Gas conduits 133A and 133B merge atcombination node 135 to become a single gas conduit 137, thus combiningthe gases from gas sources 130A and 130B. Gas conduits 133A and 133B canbe thought of as inputs to combination node 135, while gas conduit 137can be thought of as an output of combination node 135. One example ofcombination node 135 includes a simple Y-fitting of piping making up thegas conduits. Another example of combination node 135 includes a gasmanifold allowing selection of reactant and carrier gases from a varietyof gas sources. Gas conduit 137 may contain a static mixer or othermixing element to improve homogeneity of the reactant gases 127. For oneembodiment, the gas conduits 133A and 133B are not merged outside thereaction chamber. For this embodiment, the gases from gas sources 130Aand 130B are combined subsequent to heating, but within the reactionchamber 112. One example includes a heated showerhead 126 havingseparate flow channels for each reactant gas 127, thus heating thereactant gases 127 prior to combination in the reaction chamber 112.

[0034] Heaters 134A and 134B supply energy to the gas conduits 133A and133B, respectively, and thus supply energy to the flow of gases from gassources 130A and 130B, respectively. Heaters 134 may be any heater orheat exchanger capable of supplying energy to the gas conduits 133 inorder to produce a rise in temperature to the gases from gas sources130. Supplying energy to the gas conduits 133 may include passingradiation or other energy through the gas conduits 133 that is absorbedby gases within the gas conduits 133. Examples of heaters 134 includeresistive heat tracing, IR radiation sources or other electric heatersas well as direct-fired, jacketed or wrapped heat exchangers. Heatingthus involves raising the gas temperature above an ambient temperature.

[0035] Gas flow temperature sensors 136A and 136B sense the temperatureof the flow of gases from gas sources 130A and 130B, respectively. Forone embodiment, gas flow temperature sensors 136 sense the temperatureof the flow of gases directly from the gas flow. For another embodiment,gas flow temperature sensors 136 sense the temperature of one or moreportions of heaters 134 and derive the temperature of the flow of gasesfrom the heater temperatures and the theoretical approach temperaturespredicted by the physical characteristics of the heaters 134, conduits133 and reactions gases 127. For one embodiment, gas flow temperature issensed after combination of the reactant gases 127 in addition to beingsensed prior to combination as depicted in FIG. 1. For a furtherembodiment, gas flow temperature is sensed only after combination of thereactant gases 127.

[0036] Jacket 144 may be used downstream of heaters 134 to reduce anytendency of the gases to condense prior to reaching reaction chamber112. Jacket 144 may be a simple insulative jacket to control energy lossof reactant gases 127 by conduction. Alternatively, jacket 144 maycontrol energy loss by supplying additional energy input to the reactantgases 127, as described with reference to heaters 134, in addition to orin lieu of providing insulation. Heaters 134 and jacket 144 maybeseparate units, as depicted in FIG. 1, or they may be a single unitsupplying energy to reactant gases 127 before and after combination.Although not shown in FIG. 1, jacket 144, if not merely an insulativejacket, may be coupled to the control system 146, described below, forcontrol of energy input by jacket 144. In a similar manner, showerhead126 may be adapted to supply energy to the reactant gases 127, asdescribed with reference to heaters 134 and jacket 144, in addition toor in lieu of heaters 134 and jacket 144.

[0037] Jacket 144 is coupled to at least gas conduit 137 to controlenergy loss of reactant gases 127 between combination node 135 andreaction chamber 112. As shown in FIG. 1, jacket 144 may be furthercoupled to at least a portion of gas conduits 133 extending betweenheaters 134 and combination node 135.

[0038] Exhaust gases are removed from the reaction chamber 112, and avacuum may be created within the reaction chamber 112, by a gas exhaustand vacuum system 142, as is well known in the art. Also present is awafer temperature sensor 138, such as a pyrometer, which is used tomeasure the temperature of the substrate 116 through a window 140.

[0039] A control system 146 monitors and controls the various elementsthat make up the CVD system 100, such as the wafer handler 122, the gasflow control valves 132, the heaters 134, the gas flow temperaturesensors 136, the wafer temperature sensor 138, and the gas exhaust andvacuum system 142. Control system 146 is in communication with thevarious elements of CVD system 100 such that process information ispassed from these elements to control system 146 through communicationlines, and process control information is passed from control system 146to various elements of CVD system 100 through communication lines. It isnoted that communications may be bidirectional across a communicationline. Control system 146 may include distributed and centralizedcomputerized industrial process control systems, as are well known inthe art. Such control systems generally include a machine-readablemedium containing instructions capable of causing the control system, ormore directly, a processor within the control system, to monitor andcontrol the various elements coupled to the control system. Examples ofsuch machine-readable medium include random access memory (RAM), readonly memory (ROM), optical storage mediums, magnetic tape drives, andmagnetic disk drives. The machine-readable medium may be fixed, such asan installed hard drive or memory module, or removable, such as amagnetic diskette or data cartridge.

[0040] Data indicating the temperature of the substrate 116 is generatedby the wafer temperature sensor 138, and is used by the control system146 to adjust the intensity of the light sources 128 so as to produce adesired wafer temperature. Data indicating the temperature of the gasflow from gas sources 130 is generated by the gas flow temperaturesensors 136, and is used by the control system 146 to adjust the energyinput of heaters 134, jacket 144 (if not a simple insulative jacket)and/or the flow rate of flow control valves 132 (reductions in flow ratecan be used to increase the gas flow temperature at a given energyinput).

[0041] In addition, multiple wafer temperature sensors 138 may be usedto sense the temperature of different regions of the substrate 116. Thatdata may be used by the control system 146 to selectively adjust theintensity of some of the light sources 128 so as to compensate foruneven heating of the substrate 116. The control system 146 alsocontrols when and what gases are provided to the showerhead 126, as wellas when exhaust gases are removed from the reaction chamber 112, in aknown manner.

[0042] The operation of the CVD system 100 will be described withreference to the deposition of titanium nitride (TiN) from titaniumtetrachloride (TiCl₄) and ammonia (NH₃). However, the invention is notlimited to this chemical system. Other reactant gases may utilized toform layers of TiN as well as layers having other compositions.

[0043] For one embodiment, gas source 130A provides titaniumtetrachloride and gas source 130B provides ammonia. Flow control valve132A controls the flow of titanium tetrachloride from gas source 130A asdirected by control system 146 in response to a desired titanium nitridedeposition rate. Flow control valve 132B controls the flow of ammoniafrom gas source 130B as directed by control system 146 in response tothe desired titanium nitride deposition rate. Gas flow may be directlycontrolled by the control system 146 by producing a set opening of aflow control valve 132 based on a desired deposition rate.Alternatively, gas flow may be indirectly controlled by the controlsystem 146 by utilizing a feedback controller (not shown) and producinga flow rate setpoint for the feedback controller which, in turn,controls the opening of a flow control valve 132. Control of gas flowsmay be responsive to other factors in addition to or in lieu of adesired deposition rate. As one example, flow of titanium tetrachloridemay be responsive to a desired deposition rate while flow of ammonia maybe responsive to a desired ammonia concentration in the reaction chamber112. To extend this example, the flow of ammonia may have a maximumlimit such that an ammonia concentration calling for ammonia flow ratesabove the maximum limit may direct a reduction in titanium tetrachlorideflow rate despite being lower than expected for the desired depositionrate. As a further example, control of both flow rates may be responsiveto desired concentrations within the reaction chamber 112.

[0044] Energy is supplied by heaters 134A and 134B to the gases from gassources 130A and 130B, respectively, prior to combination of the gasesfor this embodiment. It is generally preferred to heat the gases priorto combination in order to reduce the probability of forming an adductor inclusion complex of the gas molecules. Combining gases cold may leadto formation of an adduct. It is preferred to avoid forming an adduct asthe adduct may require excessive or undesirable energy input to breakthe association of the individual gas molecules. Adducts having anegative effect on deposition may form between a precursor and otherconstituents of the reactant gases, e.g., another precursor or a carriergas.

[0045] For one embodiment, one or more of the gases from gas sources130A and 130B are heated to a temperature below the auto-reactiontemperature, or the lowest temperature at which at least one precursorwill react without further energy input, prior to introduction to thereaction chamber 112. For another embodiment, the gases from gas sources130A and 130B are each heated to a temperature within approximately 150°C. of the auto-reaction temperature prior to introduction. For a furtherembodiment, the gases from gas sources 130A and 130B are each heated toa temperature within approximately 50° C. of the auto-reactiontemperature prior to introduction.

[0046] For yet another embodiment, one or more of the gases from gassources 130A and 130B are heated to a temperature at or above which theygenerally will not form an adduct when combined. For a furtherembodiment, the gases from gas sources 130A and 130B are each heated,prior to combination, to a temperature at least approximately 50° C.above the temperature at which they generally will not form an adduct.It is recognized that the auto-reaction temperature and the temperatureabove which the gases will generally not form an adduct are dependentupon the pressure chosen for operation of the CVD system 100.

[0047] When only one reactant gas is heated, its temperature should bechosen such that, when combined with other reactant or carrier gases, noadduct will form and auto-reaction will not occur. While temperaturesapproaching the auto-reaction temperature, and diverging from conditionsfavoring adducts, are preferred, the designer should recognize that hotspots within the heaters may lead to localized reaction if a temperaturetoo close the auto-reaction temperature is chosen.

[0048] For one embodiment, the temperature of each reactant gas isadjusted to be substantially equal at the time of combination. Foranother embodiment, the range of temperatures of the reactant gases hasa magnitude of at least approximately 10° C. at the time of combination.When the temperatures of the various reactant gases are notsubstantially equal at the time of combination, temperatures should bechosen such that, when combined, no adduct will form and auto-reactionwill not occur.

[0049] For an embodiment utilizing the precursors of titaniumtetrachloride and ammonia to form titanium nitride, and a CVD system 100operating at a chamber pressure of approximately 0.2-10 torr and asubstrate temperature of 450-650° C., the titanium tetrachloride and theammonia are each heated to a temperature in the range of approximately200-300° F. (90-150° C.) prior to combination. Typical flow rates underthese conditions may be 10-50 sccm for titanium tetrachloride and 50-150sccm for ammonia. For a specific embodiment, the chamber pressure isapproximately 1 torr, the substrate temperature is approximately 580°C., the titanium tetrachloride flow rate is approximately 30 sccm andthe ammonia flow rate is approximately 100 sccm. It has been reportedthat reaction of titanium tetrachloride and ammonia can be effected attemperatures as low as 200° C. Therefore, the substrate temperaturechosen to drive the reaction at the surface of the substrate should notbe confused with the auto-reaction temperature of the precursors.

[0050] For one embodiment, the temperature of the reactant gascontaining the titanium tetrachloride and the temperature of thereactant gas containing the ammonia are substantially equal at the timeof combination. For another embodiment, the difference between thetemperature of the reactant gas containing the titanium tetrachlorideand the temperature of the reactant gas containing the ammonia has amagnitude of at least approximately 10° C. at the time of combination.The temperature of the gases before and after combination is maintainedby jacket 144. For one embodiment, the temperature of the gases aftercombination is further raised by jacket 144 in accordance with the aboveguidelines relating to the auto-reaction temperature, i.e., maintainingthe gas temperature below the auto-reaction temperature prior tointroduction to the reaction chamber 112.

[0051] The heated reactant gases 127 enter the reaction chamber 112where the precursors are transported to the surface of the substrate116. The reactant gases 127 react to deposit a layer of material on thesurface of the substrate 116. In more detail, the precursors of thereactant gases 127 are adsorbed on the surface of the substrate 116where they react and deposit, in this case, titanium nitride. Heatingthe reactant gases 127 prior to introduction to the reaction chamber 112as described above has been shown to reduce the formation of ammoniumchloride in deposited titanium nitride layers, thus reducing oreliminating the need for an ammonia post-flow procedure. Reducing theformation of impurities during deposition can also permit deposition atreduced chamber temperatures, thus reducing undesirable diffusion withinthe substrate and improving the thermal budget available for subsequentprocessing. Accordingly, reactant gas preheating may be used to improvephysical characteristics of the resulting deposited layer, to improvethe physical characteristics of the underlying substrate and/or toimprove the thermal budget available for subsequent processing.Furthermore, a given impurity level may be attained at reduced thermalinput to the substrate, thus reducing undesirable diffusion of implantsin integrated circuit devices.

[0052] As noted previously, and as is well known, integrated circuitfabrication involves the deposition of a plurality of layers supportedby a substrate. The CVD processes and systems described herein may beused to form one or more of these layers. Integrated circuits aretypically repeated multiple times on each substrate. The substrate isfurther processed to separate the integrated circuits into dies as iswell known in the art.

[0053] Semiconductor Dies

[0054] With reference to FIG. 2, for one embodiment, a semiconductor die210 is produced from a wafer 200. A die is an individual pattern,typically rectangular, on a substrate that contains circuitry, orintegrated circuit devices, to perform a specific function. At least oneof the integrated circuit devices contains at least one CVD-depositedlayer formed in accordance with the invention. For one embodiment, theCVD-deposited layer formed in accordance with the invention is atitanium nitride layer. A semiconductor wafer will typically contain arepeated pattern of such dies containing the same functionality. Die 210may contain circuitry to extend to such complex devices as a monolithicprocessor with multiple functionality. Die 210 is typically packaged ina protective casing (not shown) with leads extending therefrom (notshown) providing access to the circuitry of the die for unilateral orbilateral communication and control.

[0055] One example of an integrated circuit device utilizing anembodiment of the invention in the formation of various conducting,semiconducting and insulating layers defining its circuitry is a memorydevice. As one specific example, memory devices may include layers oftitanium nitride as diffusion barrier layers in, for example, contactsand wordlines.

[0056] Memory Devices

[0057]FIG. 3 is a simplified block diagram of a memory device accordingto one embodiment of the invention. The memory device 300 includes anarray of memory cells 302, address decoder 304, row access circuitry306, column access circuitry 308, control circuitry 310, andInput/Output circuit 312. The memory can be coupled to an externalmicroprocessor 314, or memory controller for memory accessing. Thememory receives control signals from the processor 314, such as WE*,RAS* and CAS* signals. The memory is used to store data which isaccessed via I/O lines. It will be appreciated by those skilled in theart that additional circuitry and control signals can be provided, andthat the memory device of FIG. 3 has been simplified to help focus onthe invention. The circuitry of memory device 300 includes at least oneCVD-deposited layer formed in accordance with the invention. For oneembodiment, the CVD-deposited layer formed in accordance with theinvention is a titanium nitride layer.

[0058] It will be understood that the above description of a DRAM(Dynamic Random Access Memory) is intended to provide a generalunderstanding of the memory and is not a complete description of all theelements and features of a DRAM. Further, the invention is equallyapplicable to any size and type of memory circuit and is not intended tobe limited to the DRAM described above. Other alternative types ofdevices include SRAM (Static Random Access Memory) or Flash memories.Additionally, the DRAM could be a synchronous DRAM commonly referred toas SGRAM (Synchronous Graphics Random Access Memory), SDRAM (SynchronousDynamic Random Access Memory), SDRAM II, and DDR SDRAM (Double Data RateSDRAM), as well as Synchlink or Rambus DRAMs and other emerging DRAMtechnologies.

[0059] Circuit Modules

[0060] As shown in FIG. 4, two or more dies 210 may be combined, with orwithout protective casing, into a circuit module 400 to enhance orextend the functionality of an individual die 210. Circuit module 400may be a combination of dies 210 representing a variety of functions, ora combination of dies 210 containing the same functionality. One or moredies 210 of circuit module 400 contain at least one CVD-deposited layerformed in accordance with the invention. For one embodiment, theCVD-deposited layer formed in accordance with the invention is atitanium nitride layer.

[0061] Some examples of a circuit module include memory modules, devicedrivers, power modules, communication modems, processor modules andapplication-specific modules, and may include multilayer, multichipmodules. Circuit module 400 may be a subcomponent of a variety ofelectronic systems, such as a clock, a television, a cell phone, apersonal computer, an automobile, an industrial control system, anaircraft and others. Circuit module 400 will have a variety of leads 410extending therefrom and coupled to the dies 210 providing unilateral orbilateral communication and control.

[0062]FIG. 5 shows one embodiment of a circuit module as memory module500. Memory module 500 contains multiple memory devices 510 contained onsupport 515, the number depending upon the desired bus width and thedesire for parity. Memory module 500 accepts a command signal from anexternal controller (not shown) on a command link 520 and provides fordata input and data output on data links 530. The command link 520 anddata links 530 are connected to leads 540 extending from the support515. Leads 540 are shown for conceptual purposes and are not limited tothe positions shown in FIG. 5.

[0063] Electronic Systems

[0064]FIG. 6 shows an electronic system 600 containing one or morecircuit modules 400. Electronic system 600 generally contains a userinterface 610. User interface 610 provides a user of the electronicsystem 600 with some form of control or observation of the results ofthe electronic system 600. Some examples of user interface 610 includethe keyboard, pointing device, monitor or printer of a personalcomputer; the tuning dial, display or speakers of a radio; the ignitionswitch, gauges or gas pedal of an automobile; and the card reader,keypad, display or currency dispenser of an automated teller machine.User interface 610 may further describe access ports provided toelectronic system 600. Access ports are used to connect an electronicsystem to the more tangible user interface components previouslyexemplified. One or more of the circuit modules 400 may be a processorproviding some form of manipulation, control or direction of inputs fromor outputs to user interface 610, or of other information eitherpreprogrammed into, or otherwise provided to, electronic system 600. Aswill be apparent from the lists of examples previously given, electronicsystem 600 will often contain certain mechanical components (not shown)in addition to circuit modules 400 and user interface 610. It will beappreciated that the one or more circuit modules 400 in electronicsystem 600 can be replaced by a single integrated circuit. Furthermore,electronic system 600 may be a subcomponent of a larger electronicsystem.

[0065]FIG. 7 shows one embodiment of an electronic system as memorysystem 700. Memory system 700 contains one or more memory modules 500and a memory controller 710. Memory controller 710 provides and controlsa bidirectional interface between memory system 700 and an externalsystem bus 720. Memory system 700 accepts a command signal from theexternal bus 720 and relays it to the one or more memory modules 500 ona command link 730. Memory system 700 provides for data input and dataoutput between the one or more memory modules 500 and external systembus 720 on data links 740.

[0066]FIG. 8 shows a further embodiment of an electronic system as acomputer system 800. Computer system 800 contains a processor 810 and amemory system 700 housed in a computer unit 805. Computer system 800 isbut one example of an electronic system containing another electronicsystem, i.e., memory system 700, as a subcomponent. Computer system 800optionally contains user interface components. Depicted in FIG. 8 are akeyboard 820, a pointing device 830, a monitor 840, a printer 850 and abulk storage device 860. It will be appreciated that other componentsare often associated with computer system 800 such as modems, devicedriver cards, additional storage devices, etc. It will further beappreciated that the processor 810 and memory system 700 of computersystem 800 can be incorporated on a single integrated circuit. Suchsingle package processing units reduce the communication time betweenthe processor and the memory circuit.

Conclusion

[0067] Chemical vapor deposition methods utilizing preheating of one ormore of the reactant gases used to form deposited layers, chemical vapordeposition systems to perform the methods, and apparatus containingdeposited layers produced using the methods have been described herein.The reactant gases include at least one chemical vapor depositionprecursor. Heating one or more of the reactant gases prior tointroduction to the reaction chamber may be used to improve physicalcharacteristics of the resulting deposited layer, to improve thephysical characteristics of the underlying substrate and/or to improvethe thermal budget available for subsequent processing.

[0068] One example includes the formation of a titanium nitride layerwith reactant gases including the precursors of titanium tetrachlorideand ammonia. Preheating these reactant gases prior to introduction tothe reaction chamber can reduce ammonium chloride levels in theresulting titanium nitride layer, thereby reducing or eliminating theneed for post-processing to remove the ammonium chloride impurity.Chemical vapor deposition systems as described herein include one ormore heaters to raise the temperature of the reactant gases prior tointroduction to the reaction chamber.

[0069] Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement which is calculated to achieve the same purpose maybe substituted for the specific embodiments shown. Many adaptations ofthe invention will be apparent to those of ordinary skill in the art.For example, a chemical vapor deposition system may further include aheater for a carrier gas to raise the temperature of the carrier gasprior to combination with a precursor gas or other reactant gas.Furthermore, the heated carrier gas may be combined with a first,unheated, reactant gas, with the heated carrier gas supplying the energyinput necessary to raise the temperature of the combined reactant gas toa desired level in lieu of direct heating of the first reactant gas.Accordingly, this application is intended to cover any adaptations orvariations of the invention. It is manifestly intended that thisinvention be limited only by the following claims and equivalentsthereof.

What is claimed is:
 1. A chemical vapor deposition system, comprising: a gas source; a reaction chamber; a gas conduit coupled between the gas source and the reaction chamber; a heater; a gas flow temperature sensor coupled to the gas conduit between the heater and the reaction chamber; and a control system coupled to the gas flow temperature sensor and the heater, wherein the control system is adapted to adjust energy input from the heater to the gas conduit in response to data from the gas flow temperature sensor.
 2. The chemical vapor deposition system of claim 1, further comprising: a second gas source; a second gas conduit coupled between the second gas source and the reaction chamber; a second heater; a second gas flow temperature sensor coupled to the second gas conduit between the second heater and the reaction chamber; wherein the control system is further coupled to the second gas flow temperature sensor and the second heater; and wherein the control system is further adapted to adjust energy input from the second heater to the second gas conduit in response to data from the second gas flow temperature sensor.
 3. The chemical vapor deposition system of claim 1, further comprising: a gas flow control valve coupled to the gas conduit; wherein the control system is further coupled to the gas flow control valve; and wherein the control system is further adapted to control an opening of the gas flow control valve in response to data from the gas flow temperature sensor.
 4. The chemical vapor deposition system of claim 1, wherein the reaction chamber has a bottom and side walls lined with quartz.
 5. The chemical vapor deposition system of claim 1, wherein the heater is a heater selected from a group consisting of resistive heat tracing, IR radiation sources, electric heaters, and wrapped heat exchangers.
 6. The chemical vapor deposition system of claim 1, wherein the chemical vapor deposition system further includes multiple wafer temperature sensors coupled to the control system.
 7. A chemical vapor deposition system, comprising: a gas source; a reaction chamber; a gas conduit coupled between the gas source and the reaction chamber; a heater; a gas flow temperature sensor coupled to the gas conduit between the heater and the reaction chamber; a gas flow control valve coupled to the gas conduit; and a control system coupled to the gas flow temperature sensor, the heater and the gas flow control valve, wherein the control system is adapted to control at least one element selected from the group consisting of the heater and the gas flow control valve in response to data from the gas flow temperature sensor, wherein control of the heater comprises adjusting energy input from the heater to the gas conduit and control of the gas flow control valve comprises adjusting an opening of the gas flow control valve.
 8. The chemical vapor deposition system of claim 7, wherein the reaction chamber has a bottom and side walls lined with quartz.
 9. The chemical vapor deposition system of claim 7, wherein the heater is a heater selected from a group consisting of resistive heat tracing, IR radiation sources, electric heaters, and wrapped heat exchangers.
 10. The chemical vapor deposition system of claim 7, wherein the chemical vapor deposition system further includes multiple wafer temperature sensors coupled to the control system.
 11. The chemical vapor deposition system of claim 7, wherein the chemical vapor deposition system further includes a plurality of light sources located within the reaction chamber for heating a substrate mounted therein.
 12. A chemical vapor deposition system, comprising: a first gas source; a second gas source; a reaction chamber; a first gas conduit coupled to the first gas source; a second gas conduit coupled to the second gas source; a first heater coupled to the first gas conduit; a second heater coupled to the second gas conduit; and a combination node having the first and second gas conduits as inputs and a third gas conduit as an output, wherein the third gas conduit is coupled to the reaction chamber.
 13. The chemical vapor deposition system of claim 12, wherein the chemical vapor deposition system further includes a gas flow temperature sensor coupled to one or more portions of the first heater, wherein the gas flow temperature sensor senses a temperature of the one or more portions of the first heater and derives a temperature of a gas flow in the first gas conduit based on the sensed temperatures of the one or more portions of the first heater and physical characteristics of the first heater, the first gas conduit, and gases in the gas flow.
 14. The chemical vapor deposition system of claim 12, wherein the first heater is a heater selected from a group consisting of resistive heat tracing, IR radiation sources, electric heaters, and wrapped heat exchangers.
 15. The chemical vapor deposition system of claim 12, wherein the chemical vapor deposition system further includes multiple wafer temperature sensors coupled to the control system.
 16. The chemical vapor deposition system of claim 12, wherein the chemical vapor deposition system further includes a plurality of light sources located within the reaction chamber for heating a substrate mounted therein.
 17. The chemical vapor deposition system of claim 12, wherein the combination node includes a Y-fitting of piping making up the first, the second, and the third gas conduits.
 18. The chemical vapor deposition system of claim 12, wherein the combination node includes a gas manifold allowing selection of gases from multiple gas sources.
 19. The chemical vapor deposition system of claim 12, wherein the chemical vapor deposition system further includes a gas exhaust and vacuum system coupled to the reaction chamber and coupled to the control system by communication lines.
 20. The chemical vapor deposition system of claim 12, wherein the third gas conduit contains a mixing element to provide homogeneity to gases introduced into the third gas conduit.
 21. A chemical vapor deposition system, comprising: a first gas source; a second gas source; a reaction chamber; a first gas conduit coupled between the first gas source and the reaction chamber; a second gas conduit coupled between the second gas source and the reaction chamber; a first gas flow temperature sensor coupled to the first gas conduit; a second gas flow temperature sensor coupled to the second gas conduit; a first heater; a second heater; and a control system coupled to the first and second gas flow temperature sensors and the first and second heaters, wherein the control system is adapted to adjust energy input from the first heater to the first gas conduit in response to data from the first gas flow temperature sensor and to adjust energy input from the second heater to the second gas conduit in response to data from the second gas flow temperature sensor.
 22. The chemical vapor deposition system of claim 21, wherein the reaction chamber has a bottom and side walls lined with quartz.
 23. The chemical vapor deposition system of claim 21, wherein the first heater is a heater selected from a group consisting of resistive heat tracing, IR radiation sources, electric heaters, and wrapped heat exchangers.
 24. The chemical vapor deposition system of claim 21, wherein the chemical vapor deposition system further includes multiple wafer temperature sensors coupled to the control system.
 25. The chemical vapor deposition system of claim 21, wherein the chemical vapor deposition system further includes a plurality of light sources located within the reaction chamber for heating a substrate mounted therein.
 26. The chemical vapor deposition system of claim 21, wherein the chemical vapor deposition system further includes a showerhead located in the reaction chamber coupled to the first gas conduit and to the second gas conduit.
 27. The chemical vapor deposition system of claim 26, wherein the showerhead is a heated showerhead having separate flow channels for each gas of multiple gas flows.
 28. A chemical vapor deposition system, comprising: a first gas source; a second gas source; a reaction chamber; a first gas conduit coupled between the first gas source and the reaction chamber; a second gas conduit coupled between the second gas source and the reaction chamber; a first gas flow temperature sensor coupled to the first gas conduit; a second gas flow temperature sensor coupled to the second gas conduit; a first heater; a second heater; a control system coupled to the first and second gas flow temperature sensors and the first and second heaters, wherein the control system is adapted to adjust energy input from the first heater to the first gas conduit in response to data from the first gas flow temperature sensor and to adjust energy input from the second heater to the second gas conduit in response to data from the second gas flow temperature sensor; a combination node having the first and second gas conduits as inputs and a third gas conduit as an output; and a jacket coupled to at least the third gas conduit.
 29. The chemical vapor deposition system of claim 28, wherein the jacket is further coupled to at least a portion of the first and second gas conduits.
 30. The chemical vapor deposition system of claim 28, wherein the jacket is an insulative jacket.
 31. The chemical vapor deposition system of claim 28, wherein the jacket is selected from the group consisting of a heater and a heat exchanger.
 32. The chemical vapor deposition system of claim 28, wherein the reaction chamber has a bottom and side walls lined with quartz.
 33. The chemical vapor deposition system of claim 28, wherein the first heater is a heater selected from a group consisting of resistive heat tracing, IR radiation sources, electric heaters, and wrapped heat exchangers.
 34. The chemical vapor deposition system of claim 28, wherein the chemical vapor deposition system further includes a plurality of light sources located within the reaction chamber for heating a substrate mounted therein.
 35. The chemical vapor deposition system of claim 28, wherein the combination node includes a Y-fitting of piping making up the first, the second, and the third gas conduits.
 36. The chemical vapor deposition system of claim 28, wherein the combination node includes a gas manifold allowing selection of gases from multiple gas sources.
 37. The chemical vapor deposition system of claim 28, wherein the combination node is located in the reaction chamber.
 38. The chemical vapor deposition system of claim 28, wherein the third gas conduit contains a mixing element to provide homogeneity to gases introduced into the third gas conduit.
 39. The chemical vapor deposition system of claim 28, wherein the chemical vapor deposition system further includes a gas exhaust and vacuum system coupled to the reaction chamber and coupled to the control system by communication lines.
 40. A computer-readable medium having computer-executable instructions for controlling a chemical vapor deposition system to provide a method of forming a layer of material on a substrate, the method comprising: controlling an environment of a reaction chamber; controlling a flow of a gas from a gas source through a gas conduit; heating the gas using a heater coupled between the gas conduit and the reaction chamber; monitoring a temperature of the gas in the gas conduit using a gas flow temperature sensor; and adjusting energy input from the heater to the gas conduit in response to data from the gas flow temperature sensor.
 41. The computer-readable medium of claim 40, wherein controlling an environment of a reaction chamber includes maintaining the walls of the reaction chamber at a temperature less than 100° C.
 42. The computer-readable medium of claim 40, wherein controlling an environment of a reaction chamber includes controlling a gas exhaust and vacuum system coupled to the reaction chamber.
 43. The computer-readable medium of claim 40, wherein controlling an environment of a reaction chamber includes adjusting an intensity of light sources located in the reaction chamber for controlling a temperature of a wafer mounted therein.
 44. The computer-readable medium of claim 40, wherein controlling a flow of a gas from a gas source includes controlling a flow control valve coupled to the gas source.
 45. The computer-readable medium of claim 40, wherein controlling a flow of a gas from a gas source includes controlling the flow of gas based on a deposition rate of the layer of material.
 46. The computer-readable medium of claim 40, wherein adjusting energy input from the heater to the gas conduit in response to data from the gas flow temperature sensor includes adjusting the energy input to maintain a gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the gas with respect to gases in the gas flow and any gases to which the gas flow is to be combined.
 47. The computer-readable medium of claim 46, wherein the layer of material is titanium nitride and the gas includes titanium tetrachloride.
 48. The computer-readable medium of claim 46, wherein adjusting the energy input to maintain a gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the gas includes adjusting energy input from the heater to the gas conduit to maintain a gas within 150° C. of an auto-reaction temperature of a chemical vapor deposition precursor in the gas.
 49. The computer-readable medium of claim 46, wherein adjusting the energy input to maintain a gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the gas includes adjusting energy input from the heater to the gas conduit to maintain a gas within 50° C. of an auto-reaction temperature of a chemical vapor deposition precursor in the gas.
 50. A computer-readable medium having computer-executable instructions for controlling a chemical vapor deposition system to provide a method of forming a layer of material on a substrate, the method comprising: controlling an environment of a reaction chamber; controlling a flow of a first gas from a first gas source through a first gas conduit; controlling a flow of a second gas from a second gas source through a second gas conduit; heating the first gas using a first heater coupled between the first gas conduit and the reaction chamber; heating the second gas using a second heater coupled between the second gas conduit and the reaction chamber; monitoring a temperature of the first gas in the first gas conduit using a first gas flow temperature sensor; monitoring a temperature of the second gas in the second gas conduit using a second gas flow temperature sensor; adjusting energy input from the first heater to the first gas conduit in response to data from the first gas flow temperature sensor; and adjusting energy input from the second heater to the second gas conduit in response to data from the second gas flow temperature sensor.
 51. The computer-readable medium of claim 50, wherein controlling an environment of a reaction chamber includes maintaining the walls of the reaction chamber at a temperature less than 100° C.
 52. The computer-readable medium of claim 50, wherein controlling an environment of a reaction chamber includes controlling a gas exhaust and vacuum system coupled to the reaction chamber.
 53. The computer-readable medium of claim 50, wherein controlling an environment of a reaction chamber includes controlling a heat source located in the reaction chamber that provides for controlling a temperature of a wafer mounted therein.
 54. The computer-readable medium of claim 50, wherein controlling a flow of a first gas from a first gas source and a flow of a second gas from a second gas source includes controlling a first flow control valve coupled to the first gas source and controlling a second flow control valve coupled to the second gas source.
 55. The computer-readable medium of claim 50, wherein controlling a flow of a first gas from a first gas source and a flow of a second gas from a second gas source includes controlling the flow of the first gas from the first gas source and the flow of the second gas from the second gas source based on a deposition rate of the layer of material.
 56. The computer-readable medium of claim 50, wherein adjusting energy input from the first heater to the first gas conduit in response to data from the first gas flow temperature sensor includes adjusting the energy input to maintain the first gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the first gas with respect to the gases in the first gas flow and the second gas flow.
 57. The computer-readable medium of claim 56, wherein adjusting energy input from the second heater to the second gas conduit in response to data from the second gas flow temperature sensor includes adjusting the energy input to maintain the second gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the second gas with respect to the gases in the first gas flow and the second gas flow.
 58. The computer-readable medium of claim 57, wherein the layer of material is titanium nitride, the first gas includes titanium tetrachloride, and the second gas includes ammonium.
 59. The computer-readable medium of claim 56, wherein adjusting the energy input to maintain the first gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the first gas includes adjusting energy input from the first heater to the first gas conduit to maintain the first gas within 150° C. of an auto-reaction temperature of a chemical vapor deposition precursor in the first gas.
 60. The computer-readable medium of claim 59, wherein adjusting the energy input to maintain the second gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the second gas includes adjusting energy input from the second heater to the second gas conduit to maintain the second gas within 50° C. of an auto-reaction temperature of a chemical vapor deposition precursor in the second gas.
 61. A computer-readable medium having computer-executable instructions for controlling a chemical vapor deposition system to provide a method of forming a layer of material on a substrate, the method comprising: controlling an environment of a reaction chamber; controlling a flow of a first gas from a first gas source through a first gas conduit; controlling a flow of a second gas from a second gas source through a second gas conduit; heating the first gas using a first heater coupled between the first gas conduit and the reaction chamber; heating the second gas using a second heater coupled between the second gas conduit and the reaction chamber; monitoring a temperature of the first gas in the first gas conduit using a first gas flow temperature sensor; monitoring a temperature of the second gas in the second gas conduit using a second gas flow temperature sensor; adjusting energy input from the first heater to the first gas conduit in response to data from the first gas flow temperature sensor; adjusting energy input from the second heater to the second gas conduit in response to data from the second gas flow temperature sensor; heating a combination of the first gas and the second gas using a jacket exchanger, wherein the first gas and the second gas are combined in a combination node having the first and second gas conduits as inputs and a third gas conduit as an output, the third gas conduit coupled to the jacket exchanger; monitoring a temperature of the combination gas in the third gas conduit using a third gas flow temperature sensor; and adjusting energy input from the jacket exchanger to the second gas conduit in response to data from the third gas flow temperature sensor.
 62. The computer-readable medium of claim 61, wherein controlling an environment of a reaction chamber includes maintaining the walls of the reaction chamber at a temperature less than 100° C.
 63. The computer-readable medium of claim 61, wherein controlling an environment of a reaction chamber includes adjusting an intensity of light sources located in the reaction chamber for controlling a temperature of a wafer mounted therein.
 64. The computer-readable medium of claim 61, wherein controlling a flow of a first gas from a first gas source and a flow of a second gas from a second gas source includes controlling the flow of the first gas from the first gas source and the flow of the second gas from the second gas source based on a deposition rate of the layer of material.
 65. The computer-readable medium of claim 61, wherein adjusting energy input from the first heater to the first gas conduit in response to data from the first gas flow temperature sensor includes adjusting the energy input to maintain the first gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the first gas with respect to the gases in the first gas flow and the second gas flow.
 66. The computer-readable medium of claim 65, wherein adjusting energy input from the second heater to the second gas conduit in response to data from the second gas flow temperature sensor includes adjusting the energy input to maintain the second gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the second gas with respect to the gases in the first gas flow and the second gas flow.
 67. The computer-readable medium of claim 66, wherein the layer of material is titanium nitride, the first gas includes titanium tetrachloride, and the second gas includes ammonium.
 68. The computer-readable medium of claim 65, wherein adjusting the energy input to maintain the first gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the first gas includes adjusting energy input from the first heater to the first gas conduit to maintain the first gas within 150° C. of an auto-reaction temperature of a chemical vapor deposition precursor in the first gas.
 69. The computer-readable medium of claim 66, wherein adjusting the energy input to maintain the second gas having at least one chemical vapor deposition precursor at a temperature below an auto-reaction temperature of each chemical vapor deposition precursor in the second gas includes adjusting energy input from the second heater to the second gas conduit to maintain the second gas within 50° C. of an auto-reaction temperature of a chemical vapor deposition precursor in the second gas.
 70. The computer-readable medium of claim 61, wherein adjusting energy input from the first heater to the first gas conduit in response to data from the first gas flow temperature sensor includes adjusting the energy input to maintain the first gas at a temperature above a temperature which reactants in the first gas and reactants in the second gas will not form an adduct when combined.
 71. The computer-readable medium of claim 70, wherein adjusting the energy input to maintain the first gas at a temperature above a temperature which reactants in the first gas and reactants in the second gas will not form an adduct when combined includes adjusting the energy input to maintain the first gas at a temperature at least about 50° C. above a temperature which reactants in the first gas and reactants in the second gas will not form an adduct when combined.
 72. The computer-readable medium of claim 70, wherein adjusting energy input from the second heater to the second gas conduit in response to data from the second gas flow temperature sensor includes adjusting the energy input to maintain the second gas at a temperature above a temperature which reactants in the first gas and reactants in the second gas will not form an adduct when combined.
 73. The computer-readable medium of claim 72, wherein the layer of material is titanium nitride, the first gas includes titanium tetrachloride, and the second gas includes ammonium. 